Growth, mortality and recruitment of Nile tilapia (Oreochromis niloticus) (L.) (Cichlidae) in Lake Turkana (Kenya): Possible variations as assessed by length frequency analysis.

Rabuor, C. O. ; Moreau, J. ; Manyala, J. O. (1998)

Estimates of growth, mortality and recruitment pattern of Nile tilapia iOreochromis niloticus) from Lake Turkana were obtained from two sets of length frequency distributions: one from HOPAON (1982) obtained in 1974 from littoral beach seining and a recent one obtained from multi-mesh size gill net fished from April 1989 to November 1991. Data analysis was performed with the FISAT (FAO ICLARM Stock Assessment Tool, version 1.0) software. Values of Lao = 40 and 59.5 (em TL), and K = 0.250 and 0.325 yr'; and the ratio of total mortality rate to the growth constant (ZlK) of 2.72 yr 5.11 y'" were obtained respectively with a clear seasonal growth pattern. The total mortality estimates from the catch curve analysis were Z = 0.96 and J .59 yr respectively with a natural mortality (M) of about 0.65 yr' for a mean environmental temperature (T) of 27°C. The highest peak for recruitment was from June to September indicating recruitment of one cohort per year. The growth performance index (0) = LoglO + 2 LoglO L"" = 2.57 and 2.87 for the two sets of data respectively. These results are discussed and compared to available information on growth performance index for Oreochromis niloticus in other large African Lakes



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